1. Field of the Invention
The invention generally relates to joint structures and methods for forming joint structures that are ideally suited for use in a vehicle body-in-white. More specifically, the invention provides both a friction welded joint assembly in which lineals and sheet, cast or extruded components are joined together and a structure and method for improving the stability of the joint structure.
2. Description of the Prior Art
It is known that various structural components for automobiles and other vehicles can be made from aluminum and other light metal alloys. Considerable development work is now underway with an objective of utilizing aluminum and other light metal alloys in the primary body structure of a vehicle or, as it is often called, the xe2x80x9cbody-in-white.xe2x80x9d An automobile chassis or body-in-white comprised of light metal alloys weighs considerably less than a steel frame that has been designed to satisfy the same requirements of safety and durability. A vehicle utilizing such a body-in-white produced from light metal alloys has improved fuel efficiency without sacrificing performance. Moreover, if the alloys utilized is an aluminum alloy, it is more easily recycled than a steel frame vehicle, and it offers improved corrosion resistance. In addition, it is known that a body-in-white utilizing space frame technology will distribute and absorb the forces encountered in the normal operation of an automobile as well as absorb and dissipate the energy of a crash or rollover.
By way of brief explanation, the space frame is a latticed framework of structural beams and columns that are joined together at their ends. These structural components of the space frame, which are sometimes referred to as lineals, are connected together by mechanical means such as bolts, rivets and clinches, by welding and adhesive bonding, and by a combination of the aforedescribed methods. Another method for connecting the lineals of a space frame is by the use of separate joining components or connecting members which are often referred to as xe2x80x9cnodesxe2x80x9d into which the lineals are designed to fit. The lineals are then securely attached to the nodes by any of the known connecting methods referred to above. An example of this technology is found in U.S. Pat. No. 4,618,163 which pertains to an automobile chassis that includes lineals and nodes. This patent is incorporated herein by reference as if fully set forth herein. If the lineals are to be joined by means of connecting members or nodes, the nodes are typically cast or otherwise formed in a separate manufacturing operation. If the lineals are to be mechanically attached to each other or to nodes by means of bolts or other fasteners appropriate holes must be provided in the several components. In the alternative, or in addition, welding, soldering, or adhesive bonding equipment and materials may be required to effect the joining of the components. Furthermore, the tolerances of the various components that are to be assembled together must be exact, in order for holes to align with other holes, or with protrusions or in order for the surfaces to fit together for welding, soldering or adhesive bonding. Finally, the complete frame is assembled in a series of discreet steps involving the joining of individual lineals to nodes or to other lineals or components in order to form subassemblies and then the subsequent joining of the various subassemblies to form the entire body-in-white space frame. As noted above, U.S. Pat. No. 4,618,163 to Hasler et al., describes an automobile space frame chassis that is made from a plurality of tubular light metal lineals that are held together by connecting members also made from light metal. Hasler et al. discloses the use of tubular members assembled by inserting their end sections into recesses in the connecting or receiving members. However, this technique has the disadvantage that the last member to be mounted in an assembly or subassembly could only be mounted by flexing or bending the structure. The elongated frame members of Hasler et al. are secured to the connecting members by welding, soldering or cementing or by the use of mechanical fasteners such as bolts, screws, and rivets.
U.S. Pat. No. 5,381,849 to Fussnegger et al. discloses a method for casting a connecting member onto the end of a hollow section such as an extruded aluminum frame member. According to this method, an end of the hollow section is placed in a mold with the end of the hollow section closed with a plug to prevent penetration of cast material therein. This method is not used to join extruded frame parts to each other but rather to join them to a cast frame member. These cast frame members are complicated solid structures that are formed in complicated molds. In addition, because the Fussnegger et al. castings may be of considerable size, they may add considerable weight to the frame structure formed by this method. It clearly is desirable to join together the components of a space frame by a simple process that minimizes manufacturing steps, compensates for tolerances at the joints and is economical to implement.
The invention provides a joint structure ideally suited for use in the manufacture of assemblies and subassemblies in aluminum structures. More particularly, the alternative joint structures and methods of forming joint structures facilitate the assembly of a vehicle body-in-white. The friction welded joints of this invention provide assemblies in which lineals and sheet, cast, or extruded components are joined together.
The invention includes a joint structure having a first component with a lineal member having a pair of ends, at least one second component having a surface and a boss extending from the surface and terminating in a boss face, the second component defining an opening extending through the boss, wherein the opening receives one end of the lineal member such that the boss face and the end of the lineal member are coterminous, and a cap member adapted to be mounted onto the coterminous ends of the lineal member and boss face. Preferably, the cap member is friction welded to the end of the first component and the boss face. The boss has an inside diameter which tapers from a first diameter proximate said boss face, to a second diameter distal therefrom and a gap is defined in the opening between the boss and the lineal member.
A sleeve may be received in the gap and has a first face and a second face such that when positioned in the gap, the sleeve second face is proximate the cap member. The sleeve preferably is discontinuous such that a diameter of the sleeve is variable and the second face may include means for removably engaging the sleeve with said cap member inner face such as a plurality of teeth adapted to contact the cap member. Suitable materials for the sleeve include aluminum, steel, and plastic. When the sleeve first diameter is smaller than the sleeve second diameter, the sleeve outside surface tapers in a direction opposite from the direction of taper of the boss inside diameter and includes a plurality of raised members adapted to engage the boss.
The joint structure may include another second component adapted to receive the other end of the lineal member, wherein the first component and the two second components constitute a vehicle subassembly. The first component may be an aluminum product form such as a sheet product, an extruded product, and a cast product. The second component may be an aluminum product such as a sheet product, an extruded product, and a cast product. While at least one end of the lineal member has a circular cross-section, a mid-portion between the ends may have a different cross-sectional configuration than the end having a circular cross-section. Lineal members having non-circular cross-sectional configurations in their mid-portion may be sheet products, extrusions or castings suitable as components in a vehicle body-in-white subassembly. For sheet product formed into a lineal member, a reinforcing means such as a bead may be included proximate at least one end thereof.
The present invention also includes a method of forming a joint for a vehicle body-in-white comprising the steps of (1) inserting a first component having a lineal member with a pair of ends into an opening in a second component having a surface and boss extending from the surface, the opening extending through the boss, such that an end of the boss and the one end of the lineal member are coterminous; and (2) attaching a cap member onto the coterminous one end of the lineal member and the boss end. The attaching step preferably is accomplished by friction welding. A gap may be defined between the second component boss and the lineal member, and the method may further include a step of inserting a sleeve into the gap. The sleeve may include a discontinuous ring such that a diameter of the sleeve is variable between a maximum and minimum limit. The sleeve has a first face and a second face such that when positioned between the second component boss and the first component lineal member, the second face is proximate the cap member. The sleeve discontinuous second face facilitates a break in the continuity of an interface between the sleeve second face and the cap member during the step of friction welding the joint.
Also included in the present invention is an assembly of a first component including a lineal member having a pair of ends, at least one of the ends having a circular cross-sectional configuration; a cap member having a body portion, a first face, and a second face, the cap member being attached to the circular cross-section end of the lineal member, preferably via friction welding; a structural member having a body portion defining an opening wherein the first component is received in the opening such that the cap member is fixed to an inner surface of the structural member body portion; and means for retaining the circular cross-section end of the lineal member within the second component. In one embodiment of the retaining means, a bore is defined in each of the cap member body portion and the structural member body portion and a bolt extends through the bores in the cap member and the structural member to retain the circular cross-section end of the lineal member within the structural member. Preferably, a nut is threaded onto the bolt against an outer surface of the structural member body portion. Alternatively, a stud extends from the cap member and through a bore in the structural member body portion and a nut threads onto the stud against an outer surface of the structural member body portion. In another embodiment of the retaining means, the circular cross-section end of the lineal member is retained within the structural component via a joint: such as a friction stir weld, a laser weld, and a mechanical fastener between the cap member and the structural component body portion.
The cap member may include an annular rim extending from the second face with the lineal member being friction welded to the second face within the annular rim such that the rim extends along an exterior of the lineal member. Alternatively, the annular rim itself mar be friction welded to the lineal member. In another embodiment, the cap member includes an annular welding surface extending from the cap member second face at a location spaced apart from the rim, with the lineal member being friction welded to the annular welding surface.
Finally, the present invention includes an energy absorbing member for a vehicle incorporating the above-described friction welded joints. The energy absorbing member includes an elongated crash box having at least one end with a circular cross-section and a bracket friction welded to the circular end. The bracket may include a raised portion defining a chamber with the circular end being received in the chamber and friction welded to the bracket within the chamber. Each end of the crash box may have a circular cross-sectional configuration and a bracket is friction welded to each circular end. One of the brackets may be configured to be attached to a vehicle and the other bracket may be configured to be attached to a bumper.
Another energy absorbing member of the present invention includes an elongated crash box, a beam defining a chamber, one end of the crash box being received within the chamber and fixed to an inside surface of the beam and a bracket assembly friction welded to the other end of the crash box. The end of the crash box within the chamber is friction welded to an inside surface of the beam. The bracket assembly includes (a) a bracket having a face and defining an opening receiving the other end of the crash box and (b) a cap member having a first face and a second face. The cap member second face is friction welded to the bracket face and the crash box other end. An annular recess in the bracket face surrounds the opening and a stepped-up portion of the bracket face surrounds the annular recess so the bracket face of the stepped-up portion and the cap member second face are positioned in a plane. The cap member may be engageable with a friction welding device to rotate the cap member via an opening therethrough which may be hexagonal, triangular or square. The crash box may be made from an extruded aluminum alloy and the bracket may be made from a cast or stamped aluminum alloy.